1. Searching for Higgs Triplets at CDF Chris Hays, Duke University CERN Non-SM Higgs Workshop Dec 1-2, 2004 ( ) H ++ H + H 0 Recent results Future analyses ( ) H ++ H + H 0   

2. Why Higgs Triplets? Natural expansion of Higgs sector * frequently arise in models with additional gauge groups Little Higgs Increases scale of divergences by ~10 Left-right symmetric (SU(2) L x SU(2) R x U(1) B-L x SU(3) c ) Restore parity symmetry to weak force at scale v R See-saw mechanism for light masses Left-right model phenomenology well studied * Excellent reference model for searches C. Hays, Duke University, Non-SM Higgs Workshop

3. Scenarios with Light Higgs Triplets Non-supersymmetric left-right models * Triplet masses typically proportional to v R Triplets could be observable at CDF Simplest see-saw mechanism not valid (but could still apply: e.g. add sterile neutrinos) If v R  1 TeV: Observable triplets requires scalar potential parameter tuning See-saw mechanism applicable If v R ≫  1 TeV: ( ) H R ++ H R + H R 0 ( ) H L ++ H L + H L 0 C. Hays, Duke University, Non-SM Higgs Workshop

4. Scenarios with Light Higgs Triplets Supersymmetric left-right models * Require additional Higgs multiplets or higher- dimensional operators (HDO) in the superpotential * HDO lead to light doubly-charged Higgs: m H±±  (v R 2 /M Pl ) C. Hays, Duke University, Non-SM Higgs Workshop See-saw suggests v R ~ 10 10 GeV, so m H±± ~ 100 GeV Gauge-mediated SUSY breaking: Light H R ++ Gravity-mediated SUSY breaking: Light H R ++  Also: HDO models require R-parity conservation

5. Doubly Charged Higgs Search at CDF pp production cross section dominated by Z/  exchange * Completely determined by weak coupling * W Higgstrahlung cross section depends on v L, C. Hays, Duke University, Non-SM Higgs Workshop constrained by the  parameter to be small  (m = 100 GeV) = 0.12 pb Expect H ++ to decay exclusively to leptons * No quark couplings due to charge conservation * W + W + decay constrained by  parameter L Y = ih ij (  c Li  2 H L  Lj +  c Ri  2 H R  Rj ) H L ++ Violates lepton number; new quantum number: B-L

6. Doubly Charged Higgs Search at CDF Search for H ++ decays to ee, , e  * Extremely clean signatures * Only require one ll' pair/event * Excellent discovery potential C. Hays, Duke University, Non-SM Higgs Workshop Low-mass background dominated by hadrons leptons Use m ll' < 80 GeV region to test background prediction

7. Doubly Charged Higgs Search at CDF C. Hays, Duke University, Non-SM Higgs Workshop Test hadron lepton predictions using low E T (<15 GeV) same-sign events with one lepton failing identification criteria Sample dominated by dijet events Same sign ee channel complicated by bremstrahlung in silicon detector * Bremstrahlung can convert to two electrons, one of which has the opposite sign of the prompt electron * Can result in wrong sign identification Drell-Yan a significant background Search only in region m ee > 100 GeV

8. Doubly Charged Higgs Search at CDF C. Hays, Duke University, Non-SM Higgs Workshop Luminosity and acceptance key to sensitivity * <1 event background means cross section limit is directly proportional to luminosity and acceptance  : Trigger muon has limited |  | (<1),  coverage, second muon has large coverage (|  | < ~1.4, all  ). ee: Both electrons have large  coverage, but limited |  | (<1). Falls rapidly for m<100 GeV due to cut-off e  : Combination of limited electron and muon coverage reduces acceptance relative to ee and . L ~ 240 pb-1: Largest sample of any published Tevatron result! Very high acceptances! Trigger and identification efficiencies included

9. Doubly Charged Higgs Search at CDF C. Hays, Duke University, Non-SM Higgs Workshop No events observed in signal regions Set 95% C.L. cross section x BR limits Assuming exclusive decays to a given channel, set mass limits: H L ±±  : m > 136 GeV H L ±± e  : m > 115 GeV H L ±± ee: m > 133 GeV H R ±±  : m > 113 GeV For diagonal couplings of equal magnitude, results correspond to the following approximate limit: H L ±± : m > 120 GeV

10. Doubly Charged Higgs Search at CDF C. Hays, Duke University, Non-SM Higgs Workshop Mass limits highest in the world for H L ±± in these channels * Sensitive to a wide range of Yukawa coupling values 10 -5 <  h ij < 0.5 Complementary to indirect searches h ij limits for m = 100 GeV: Bhabha scattering: h ee < 0.05 (g-2)  : h  < 0.25  3e: h ee h e  < 3.2 x 10 -7  e  : h  h e  < 2 x 10 -6 D. Acosta et al., PRL 93 (2004), 221802

11. Doubly Charged Higgs Search at CDF C. Hays, Duke University, Non-SM Higgs Workshop CDF has also searched for quasi-stable H ±± * Probes low Yukawa coupling values  h ij < 10 -8 Strategy: Use dE/dx information from tracker Search for pairs of high-momentum doubly-charged tracks Define tight “discovery” selection including calorimeter ionization Couplings don't exist for additional triplets that conserve lepton number

12. Doubly Charged Higgs Search at CDF C. Hays, Duke University, Non-SM Higgs Workshop dE/dx resolution provides many  separation of signal and background Background < 10 -5 Single-event discovery! Signal confirmation defined a priori Require large MIP energy in calorimeter Further suppresses muon backgrounds Backgrounds studied with data and MC < 10 -6 < 10 -9 < 10 -5 < 10 -12 < 10 -7 < 10 -9 < 10 -6 No candidates in samples used to determine acceptance Yields upper limits on expected background Calibration sample Expected signal Background

13. Doubly Charged Higgs Search at CDF C. Hays, Duke University, Non-SM Higgs Workshop Acceptance has additional inefficiencies and uncertainties (beyond  ) * Fraction of H ±± with  too small to reconstruct tracks * Multiple scattering affecting track matching to muon track segment * Ionization affecting calorimeter isolation requirements Acceptance reduced relative to  : * Both H ±± must be central, with reconstructed tracks * Additional track cuts and inefficiencies * Still > 30% L ~ 200 pb-1

14. Doubly Charged Higgs Search at CDF C. Hays, Duke University, Non-SM Higgs Workshop No events observed in data Set 95% C.L. cross section limit Infer mass limits: H L ±± : m > ~125 GeV H R ±± : m > ~100 GeV Limits similar to  and ee decay channels Sensitivity will improve with order of magnitude increase in luminosity: H L ±± : m ~ 200 GeV H R ±± : m ~ 170 GeV Left and right cross sections combined

15. Ongoing H ±± Search at CDF C. Hays, Duke University, Non-SM Higgs Workshop Same-sign tau decays Experimentally challenging: * Cannot fully reconstruct invariant mass * Hadronic tau decays difficult to detect Many problems solved in H 0  search: Studying issues of sign identification Determining backgrounds for same-sign sample Phenomenologically interesting: * h  coupling the least constrained

16. Other Possible Triplet Searches at CDF C. Hays, Duke University, Non-SM Higgs Workshop Same final state as H 0 WW search Can reoptimize for leptons from H ± decays NLO cross section would help in full analysis H ± : * Experimentally accessible * No quark couplings if no mixing with Higgs doublet

17. Other Possible Triplet Searches at CDF C. Hays, Duke University, Non-SM Higgs Workshop H ±±, H ± : * Existing searches have sensitivity * Signatures depend on NLSP   1 0 : H ±± ll' l  1 0 l' l  0  0 l' H ± l l  1 0 l  0  0 Final state lll'l'  E T Final state ll  E T l: H ±± ll' l  0 l'H ± l l  0 Final state lll'l'E T Final state llE T        Need to validate MC generators, use for optimization and acceptance determination NLO cross section would help  

18. Summary C. Hays, Duke University, Non-SM Higgs Workshop Higgs triplets a likely component of non-SM Higgs sector Arise in well-motivated models Doubly-charged Higgs searches particularly attractive Accessible to colliders in a number of scenarios Extremely clean signatures: excellent discovery potential CDF has world's highest mass limits for long-lived H ±± and decays to ee, e ,  Ongoing data-taking will significantly extend sensitivity Still early in Run 2! Potential for a range of additional triplet searches Need to determine sensitivity (cross sections, acceptances)